Yadex's homepage

Description

Yadex is a Doom level (wad) editor for Unix systems running X,
including Linux. It supports Doom alpha, Doom beta, Doom, Ultimate
Doom, Final Doom, Doom II, Heretic and also, in a more or less
limited way, Hexen and Strife. It is available under the terms of
the GPL.

Yadex is descended from DEU 5.21. Therefore, as you might expect,
it's a rather low-level editor that requires you to take care of a
lot of detail but on the flip side allows you to control very
precisely what you are doing. In addition, it has many advanced
functions that DEU didn't have, to make certain tedious tasks easy.